1. Field of the Invention
The invention relates to radar antenna systems and more particularly to rotating couples to accommotate antenna mechanical rotation.
2. Description of the Prior Art
In the prior art rotating RF couplings have been provided in a number of forms. A brief summary of their use is contained in the test Radar Handbook by Merrill I. Skolnik (McGraw-Hill 1970) in Chapter 8 under a paragraph entitled "Rotary Joints." Bibliographical references concerning the theory and design of rotary joints are contained in that summary.
The patent literature also includes description of prior art devices of conventional type, such as the apparatus of U.S. Pat. No. 2,751,559, for example.
In U.S. Pat. No. 3,896,446, a rotating RF joint is involved in a scanning radar system in which the antenna system is mounted over the top of a helicopter rotor to rotate with it, however, no advances in the rotary joint itself appear to be disclosed.
Other rotary RF joints, such as shown in U.S. Pat. No. 3,123,782 appear to be based on conductive circular ring arrangements and as such may be thought of as "slip-ring" devices.
Still further, systems not including sliding contacts but providing electromagnetic energy transfer in a rotating joint include multihorn configurations and the like. U.S. Pat. No. 3,803,619, and also U.S. Pat. Nos. 3,117,291 and 3,108,235 disclose devices of that type.
The slip-ring systems present well-known arcing, mechanical wear, and other problems, and the rotating horn devices are complex and costly, and also leave much to be desired in energy transfer efficiency.
In the most familiar shipboard rotating antenna installations, lateral structural members affixed to mast structures have been required. Prior art rotary joints of the aforementioned and other conventional types have been applied in such instances. Many have used such expedients as circular waveguide, coaxial transmission line sections and the like providing rotatable conductive walls essentially concentric with the axis of rotation of the antenna structure itself.
The manner in which the invention advances the art relating RF (microwave) rotary joints will be understood as this description proceeds.